Blood Red Skies vs Sunset Red

How close are they?

ΔE 29.4, loose: different enough that you should pick on purpose. Sunset Red is noticeably darker, much more muted, cooler than Blood Red Skies.

Can I use Sunset Red instead of Blood Red Skies?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Sunset Red is noticeably darker, much more muted, cooler than Blood Red Skies.

Can I use Blood Red Skies instead of Sunset Red?

The same difference applies the other way round: Blood Red Skies is noticeably lighter, much more saturated, warmer.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.